DateTime group by date and hour

I have a datetime called activity_dt and the data looks like this:

2/5/2013 9:24:00 AM
2/7/2013 7:17:00 AM

How do i group by date and hour?

mysql
sql

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SELECT [activity_dt], COUNT(*) as [Count]
FROM
(SELECT dateadd(hh, datediff(hh, '20010101', [activity_dt]), '20010101') as [activity_dt]
FROM table) abc
GROUP BY [activity_dt]

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最佳答案

SQL Server :

SELECT [activity_dt], count(*)
FROM table1
GROUP BY DATEPART(day, [activity_dt]), DATEPART(hour, [activity_dt]);

Oracle :

SELECT [activity_dt], count(*)
FROM table1
GROUP BY TO_CHAR(activity_dt, 'DD'), TO_CHAR(activity_dt, 'hh');

MySQL :

SELECT [activity_dt], count(*)
FROM table1
GROUP BY hour( activity_dt ) , day( activity_dt )

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Using MySQL I usually do it that way:

SELECT count( id ), ...
FROM quote_data
GROUP BY date_format( your_date_column, '%Y%m%d%H' )
order by your_date_column desc;

Or in the same idea, if you need to output the date/hour:

SELECT count( id ) , date_format( your_date_column, '%Y-%m-%d %H' ) as my_date
FROM  your_table
GROUP BY my_date
order by your_date_column desc;

If you specify an index on your date column, MySQL should be able to use it to speed up things a little.

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In my case... with MySQL:

SELECT ... GROUP BY TIMESTAMPADD(HOUR, HOUR(columName), DATE(columName))